1. Field of the Invention
The invention relates to a boost circuit and a power supply converter and, more particularly, to a boost circuit and a power supply converter capable of detecting the occurrence of a spark.
2. Description of the Related Art
Coupled with the development of the optoelectronic industry, luminescent sources are not only utilized in daily life lighting, but smaller luminescent sources (LCD lamps for instance) are also being extensively applied in various electronic products. Take the LCD display for example, it is provided with a luminescent source used as the backlight.
Generally, a power supply converter is needed to light a lamp. A conventional power supply converter is chiefly consisted of an oscillator and a boost circuit. The oscillator produces an alternating current frequency required by the lamp, and the boost circuit produces a voltage high enough to activate the lamp.
Referring to FIG. 1, a conventional boost circuit 1 is chiefly consisted of a sensing resistor RS used to sense loop currents, a converter T used to convert voltages and a capacitor C used to store voltages. In FIG. 1, the symbol 2 represents a connector, and the symbol 3 represents a lamp. In other words, the lamp 3 is connected with the boost circuit 1 via the connector 2.
With respect to the above structure, if the connection between the lamp 3 and the connector 2 is not sound, a spark occurs within the boost circuit 1 due to the loose contact. Moreover, if short-distance breakage exists within the boost circuit 1, or the winding in the converter T of the boost circuit is disconnected, a spark is also brought about. Also, if a particular conductor in the product is situated too close to the boost circuit 1, a spark occurs as well.
For the reason that when a spark occurs within products of the early days, common lamps are still able to luminesce normally. The phenomenon is not easily detected based upon the product appearances or quality of image, and therefore, without inspecting the products before they become commercially available, they may result in some undesirable situations such as shortening the life of products. In worse cases, serious disasters may be caused if the spark come into contact with combustible gases (circumstances such as products are located at gas stations).
To determine whether a spark occurs within the product, a sensing resistor is commonly used for detection, that is, the output voltage waveform at the point A shown in FIG. 1 is detected to decide if the boost circuit is normal. However, whether a spark occurs within the boost circuit cannot be accurately detected merely using such a method. Referring to FIG. 2A, when a spark occurs within the boost circuit, theoretically inrush signals a1 and a2 are supposed to be detected at the point A. Nevertheless, it is observed from FIG. 2A that by using the conventional detecting method, the inrush signals a1 and a2 are possibly hidden within the output waveform and are not apparently perceived. Therefore, defective products may become commercially available, thereby causing hazards when using them.
In view of the above issues, to authentically detect products that have sparks and so as to prevent them from becoming commercially available, or to activate protection mechanisms when sparks occur within the products, is a vital task. To sum up, how to provide a boost circuit or power supply converter that is able to accurately detect the occurrence of sparks is an essential topic.
One object of the invention is to provide a boost circuit that is able to accurately detect the occurrence of a spark.
Another object of the invention is to provide a power supply converter that is able to accurately detect the occurrence of a spark.
The feature of the invention is to employ the high pass property of capacitance, to detect inrush signals produced by a boost circuit or power supply converter, thereby accurately determining the occurrence of a spark.
To accomplish the above objects, the present invention provides a boost circuit including a first capacitor, a transformer, a sensing resistor and a second capacitor. The transformer has a boost side coil with its one end connected in series with the first capacitor and the other end connected in series with the sensing resistor. One end of the second capacitor is connected in parallel with the transformer.
Also, the invention provides a power supply converter including a boost circuit and a detection circuit. The boost circuit is used to produce a voltage and output a detection signal for spark detection. The detection circuit is electrically connected with the boost circuit to receive the detection signal output by the boost circuit. When the detection circuit detects that the detection signal contains an inrush signal, it determines that spark is occurring within the boost circuit and outputs a control signal according to the inrush signal.